Actually, all specialty shops selling such items would probably hold one. You can find such shops almost anywhere nowadays. The most prominent ones are Condomania at the basement of Lucky Plaza. There is also another one in Midpoint Orchard Level 3 or 4.

That said, a walk along Geylang Road should let you pass by a few of such shops. Too shy to walk in, eh? If you ain't you'd have found them by now.